Tech Tip

Tech Tip Number: TT707.001
Product: Series 707 Super Voyager VLB-III
Revision: All revision levels
Frequency: All frequencies
Date: June 24, 1994
Released By: Documentation Control

Subject: COM2 port problem on Series 707 motherboards

Problem:

Serial port 2 (COM2) does not function correctly if the Series 707
motherboard has BIOS Release 707041894. The BIOS version number appears on
the boot screen.

Reason:

The series 707 system BIOS does not enable or disable the COM2 and COM1
FIFO buffer correctly.

The COM1 FIFO buffer is always disabled by the Series 707 system BIOS
Release 707041894 and this FIFO buffer cannot be enabled through WinBIOS
Setup. This initialization failure should not be a problem because
Microsoft Windows, OS/2, and other operating systems initialize the FIFO
buffers directly.

However, the COM2 FIFO buffer is always enabled by the Series 707 system
BIOS Release 707041894 and this FIFO buffer cannot be disabled through
WinBIOS Setup. Enabling the COM2 FIFO buffer will cause problems if a
mouse is connected to COM2.

Solutions:

There are three possible solutions:

1. Use either a PS/2 mouse or attach the mouse to COM1 and disable COM2.

With this solution, you can still attach a high speed modem to COM2
because the FIFO buffer must be enabled for the modem to work properly. A
serial printer can also be attached to COM2 if the serial printer will
work correctly with the COM2 FIFO buffer enabled.

2. Use FIFO-OFF.COM

The FIFO-OFF.COM file can be installed in AUTOEXEC.BAT and can be
automatically loaded at system boot. This program disables the COM2 FIFO
buffer. This solution is required if a mouse is attached to COM2.
FIFO-OFF.COM is available on the American Megatrends BBS.

A mouse cannot be used with WinBIOS Setup if this solution is implemented,
because the COM2 FIFO buffer is enabled. However, the WinBIOS Setup
keyboard commands will still work and all WinBIOS Setup functions can be
performed through the keyboard.

3. Use a new system BIOS

Use Series 707 BIOS Release 707062494, available from American Megatrends.
This BIOS release corrects the COM port problem.

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Caution: Do not enable FIFO buffers for COM ports that are used for the mouse.
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